This invention relates to a torsion spring assembly having a torsion spring which, when loaded torsionally, exerts a biasing force on a member associated with the spring. The invention more particularly relates to a torsion spring of the type which is defined by a plurality of helically wound coils and by two radially projecting end tangs, the spring being loaded torsionally when one of the end tangs is moved angularly relative to the other end tang.
While the spring assembly of the invention may be used in various applications, it is particularly suitable for use in effecting closure of the throttle valve of the throttle body or carburetor of an automotive internal combustion engine. A spring assembly of this general type is disclosed in Paggeot U.S. Pat. No. 4,828,235. In that assembly, two flanged bushings are telescoped into the end portions of the spring and mount the spring on the shaft of the throttle body. The end coils of the spring are of reduced diameter and are capable of tightly gripping the bushings in order to hold the bushings in assembled relation with the spring.
By virtue of the bushings, the coils of the spring of the Paggeot spring assembly are held in concentric relation with the shaft so that, when wound, the coils remain substantially uniform without substantial canting and without causing any substantial friction, sawing action or wear. While the spring assembly functions admirably in many applications, it does suffer some draw backs. In some cases, it is necessary that all of the spring coils be fully active in order to achieve a specified spring rate with acceptable endurance stress levels. Because the end coils of the Paggeot spring are contracted around the bushings in order to keep the bushings assembled with the spring, the end coils are not fully active. Also, it is somewhat difficult to assemble the spring and bushings of the Paggeot spring assembly.